Abstract

Prenatal testosterone (T) treated female sheep display reproductive deficits similar to women with polycystic ovary syndrome (PCOS), including an increase in luteinizing hormone (LH) pulse frequency due to actions of the central gonadotropin-releasing hormone (GnRH) pulse generator. Here we used multiple-label immunocytochemistry to investigate the possibility of changes in the GABA neurotransmitter system at two key components of the GnRH pulse generator in prenatal T sheep: Kisspeptin/Neurokinin B/Dynorphin (KNDy) neurons of the arcuate nucleus, and GnRH neurons in the preoptic area (POA) and medial basal hypothalamus (MBH). We observed a significant decrease and increase, respectively, in the number of GABAergic synapses onto POA and MBH GnRH neurons in prenatal T ewes; in addition, there was a significant increase in the number of GABAergic inputs onto KNDy neurons. To determine the actions of GABA upon GnRH and KNDy neurons, we examined co-localization with the chloride transporters, NKCC1 and KCC2, which indicate stimulatory or inhibitory activation of neurons by GABA, respectively. The majority of GnRH neurons in both POA and MBH co-localized NKCC1 transporters while none contained the KCC2 transporter. A majority of KNDy neurons co-localized either NKCC1 or KCC2, and 28% of the KNDy population contained NKCC1 alone. Therefore, we suggest that, as in the mouse, GABA in the sheep is stimulatory to GnRH neurons, as well as to a subset of KNDy neurons. Increased numbers of stimulatory GABAergic inputs to both MBH GnRH and KNDy neurons in prenatal T animals may contribute to alterations in steroid feedback control and increased GnRH/LH pulse frequency seen in this animal model of PCOS.